2.4 Monitoring Faults

Outline

Devices that monitor faults

• Geologists have invented instruments that can record ground movements
  • Creep meters
    • Wires are stretched across a fault to measure the movement of the fault horizontally
    • One side is held by a post while the other is held by a weight that moves when the fault moves.
  • Laser-ranging devices
    • A laser is used to detect even the tiniest of fault movements
    • If the laser is delayed even by a fraction of a second, a device detects the change and marks it.
  • Tilt-meters
    • Measures the tilting ground
    • There are two bulbs, each filled with water, that move from one side to another when the fault rises or falls
    • Each bulb contains a measuring device to measure the liquid
  • Satellite Monitors
    • Satellites are equipped with radar to take picture of faults
    • The satellite sends radio waves to the Earth and, when the waves come back in, marks the time
    • If times vary, geologists can take a look at the photos to see slight changes in elevation

Monitoring Risk in the U.S.A

• Scientists cannot accurately predict earthquakes
• Geologists use the knowledge that earthquakes occur wherever plate movement stores energy along faults
• Geologists determine they can find where an earthquake can occur based where past earthquakes have happened
  • Most likely to be hit with an earthquake that is Major.
    • San Francisco
    • Los Angeles
    • Salt Lake City
    • Charleston
    • Boston
    • Seattle
  • Most likely to be hit with an earthquake that is moderate.
    • Phoenix
    • St. Louis
    • Atlanta
    • Cleveland
  • Most likely to be hit with an earthquake that is minor.
    • Denver
    • Minneapolis
    • Chicago
    • New Orleans
    • Cleveland
    • Washington D.C
    • Philadelphia
    • New York
  • Area where earthquakes never strike.
    • Houston
    • Miami